The present invention concerns a device for stopping the deployment of an airbag in a vehicle.
In order to protect the life of passengers in a traffic accident, modern vehicles are often equipped with a protection system comprising several airbags which serve to absorb the energy of a passenger released on the impact of the accident. A deceleration detector detects the impact and operates one or more inflation devices in order to fill the airbag with a gas and deploy it between the occupant of the car and the parts of the bodywork surrounding the dashboard which might injure the occupant.
In order to prevent injuries caused by the airbag itself, it is advantageous to stop the deployment of the airbag once the airbag is close enough to the passenger or when the passenger has sunk sufficiently into the airbag for the airbag to be able to perform its absorbing action. By stopping the deployment of the airbag in this way, it is possible to prevent the pressure exerted by the deployed airbag on the passenger from increasing in an uncontrollable manner.
For protection systems in which the airbag is inflated by several inflators operated successively, a known device exists to stop the deployment of the airbag comprising several metal conductors of different lengths, integrated within the front wall of the airbag, i.e. in the wall of the airbag facing the passenger. Each metal conductor is linked to the inflator operating device so that the breakage of a conductor triggers the operation of an inflator associated to that conductor. As the airbag deploys itself, the front wall of the airbag unfolds and the conductors successively break, thus triggering the operation of the next inflator. When the volume of the airbag is such that the airbag touches the passenger, the front wall of the airbag no longer unfolds and the next conductor does not break. It is thus possible to prevent the next inflator from operating and the pressure exerted by the airbag on the passenger from increasing too much.
Another method of stopping the deployment of the airbag is to control its speed of deployment. This can be achieved by a wire having along its entire length a coding of alternate colours, which is fixed on one side to the inside of the airbag on the front face of the latter. The wire passes through an optical detector which, when the airbag is deployed, detects the speed at which the wire passes through with the aid of the coding e.g. black and white. When the front face no longer moves away from the optical detector, i.e. when the volume of the airbag is such that the front wall touches the passenger, the speed of passage of the wire through the detector becomes zero. The airbag operating device then stops the inflator and/or opens a vent in the airbag so that the latter inflates no further.
The two systems described above, detecting by different methods the collision of the airbag with the occupant of the vehicle, only work if the passenger sufficiently checks the deployment of the airbag for the systems to be triggered. Now a child or a light adult is often of insufficient weight to stop the deployment of the airbag. Consequently, the protection systems do not operate and the deployment of the airbag continues even though a strong pressure is exerted between the airbag and the occupant of the vehicle.
In order to remedy this situation, Document GB-A-2319997 describes a system for stopping the deployment of an airbag in a vehicle, which comprises a proximity detector located on the front face of the airbag. The proximity detector makes it possible to detect the distance of the airbag in relation to an occupant of the vehicle and generates a distance signal which is sent to an airbag operating device. When a certain distance between the airbag and the occupant is reached, the operating device stops the deployment of the airbag. On the one hand such a system makes it possible to prevent the passenger from being injured by the airbag due to bad positioning, on the other this system risks stopping the deployment of the airbag before the latter can perform its shock absorbing function.
The aim of the present invention is to propose an improved system for stopping the deployment of an airbag in a vehicle.